WO2005097502A1 - Elements d'impression possedant des couches de transition de solubilite et procedes associes - Google Patents

Elements d'impression possedant des couches de transition de solubilite et procedes associes Download PDF

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Publication number
WO2005097502A1
WO2005097502A1 PCT/US2005/010193 US2005010193W WO2005097502A1 WO 2005097502 A1 WO2005097502 A1 WO 2005097502A1 US 2005010193 W US2005010193 W US 2005010193W WO 2005097502 A1 WO2005097502 A1 WO 2005097502A1
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WO
WIPO (PCT)
Prior art keywords
layer
imaging
ink
substrate
adhere
Prior art date
Application number
PCT/US2005/010193
Other languages
English (en)
Inventor
Eugene L. Langlais
Kenneth R. Cassidy
Original Assignee
Presstek, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Presstek, Inc. filed Critical Presstek, Inc.
Priority to JP2007505242A priority Critical patent/JP2007531019A/ja
Priority to AU2005231729A priority patent/AU2005231729A1/en
Priority to CA002560644A priority patent/CA2560644A1/fr
Priority to DE602005007336T priority patent/DE602005007336D1/de
Priority to EP05731303A priority patent/EP1732758B1/fr
Publication of WO2005097502A1 publication Critical patent/WO2005097502A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C1/00—Forme preparation
    • B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
    • B41C1/1008—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by removal or destruction of lithographic material on the lithographic support, e.g. by laser or spark ablation; by the use of materials rendered soluble or insoluble by heat exposure, e.g. by heat produced from a light to heat transforming system; by on-the-press exposure or on-the-press development, e.g. by the fountain of photolithographic materials
    • B41C1/1016—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by removal or destruction of lithographic material on the lithographic support, e.g. by laser or spark ablation; by the use of materials rendered soluble or insoluble by heat exposure, e.g. by heat produced from a light to heat transforming system; by on-the-press exposure or on-the-press development, e.g. by the fountain of photolithographic materials characterised by structural details, e.g. protective layers, backcoat layers or several imaging layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
    • B41N1/00—Printing plates or foils; Materials therefor
    • B41N1/04—Printing plates or foils; Materials therefor metallic
    • B41N1/08—Printing plates or foils; Materials therefor metallic for lithographic printing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
    • B41N1/00—Printing plates or foils; Materials therefor
    • B41N1/04—Printing plates or foils; Materials therefor metallic
    • B41N1/08—Printing plates or foils; Materials therefor metallic for lithographic printing
    • B41N1/083—Printing plates or foils; Materials therefor metallic for lithographic printing made of aluminium or aluminium alloys or having such surface layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2201/00—Location, type or constituents of the non-imaging layers in lithographic printing formes
    • B41C2201/04—Intermediate layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/02—Positive working, i.e. the exposed (imaged) areas are removed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/04—Negative working, i.e. the non-exposed (non-imaged) areas are removed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/08—Developable by water or the fountain solution
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/14—Multiple imaging layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/22—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by organic non-macromolecular additives, e.g. dyes, UV-absorbers, plasticisers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/24—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by a macromolecular compound or binder obtained by reactions involving carbon-to-carbon unsaturated bonds, e.g. acrylics, vinyl polymers

Definitions

  • a printable image is present on a printing member as a pattern of ink-accepting (oleophilic) and ink-rejecting (oleophobic) surface areas. Once applied to these areas, ink can be efficiently transferred to a recording medium in the imagewise pattern with substantial fidelity.
  • the non-image areas are -hydrophilic, and the necessary ink-repellency is provided by an initial application of a dampening fluid to the plate prior to inking. The dampening fluid prevents ink from adhering to t_he non-image areas, but does not affect the oleophilic character of the image areas.
  • Ink a-pplied uniformly to the wetted printing member is transferred to the recording medium only in the imagewise pattern.
  • the printing member first makes contact with a compliant intermediate surface called a blanket cylinder which, in turn, applies the image to the pa_per or other recording medium.
  • the recording medii-xm is pinned to an impression cylinder, which brings it into contact with the blanket cylinder.
  • Plate-imaging devices amenable to computer control include various forms of lasers.
  • the present invention utilizes solubility transitions rather than ablation mechanisms to facilitate selective removal of the imaging layer of a lithographic plate, which allows for imaging with low-power lasers that need not impart ablation-inducing energy levels.
  • the invention involves a printing member having a first layer that is permeable to an aqueous solution, a second layer thereunder, and a substrate beneath the second layer. At least a portion of the second layer undergoes a transition from an insoluble state to a soluble state in response to heat; the change in solubility may be with respect to water or another solvent.
  • the substrate and the first layer can have the same or opposite affinities for ink and/or a liquid to which ink will not adhere.
  • first and second layers can have the same or opposite affinities for ink and/or a liquid to which ink will not adhere.
  • the transition the second layer undergoes may involve a transition from a crystalline state to an amorphous state.
  • Polyvinyl alcohol is a suitable material for this purpose.
  • Substantially all, or only a portion of the second layer exposed to the imaging radiation may undergo the transition.
  • the substrate may be fabricated from a metal or a polymer.
  • the first layer may contain a material, such as a pigment or dye, that absorbs imaging radiation and transfers thermal energy to the second layer.
  • the second layer may contain such a pigment or dye, or it may be present in both layers.
  • the printing member contains a third layer between the second layer and the substrate.
  • the printing member may contain a top layer above the first layer that is permeable to a solvent (e.g., an aqueous fluid), is transparent to imaging radiation, and has the same affinity as the first layer for ink and/or a liquid to which ink will not adhere.
  • a solvent e.g., an aqueous fluid
  • the invention involves a method of imaging the lithographic printing member described above. The printing member is exposed to imaging radiation in an imagewise pattern, which causes at least a portion of the second layer exposed to the radiation to undergo a transition from an insoluble state to a soluble state.
  • the printing member is next subjected to a solvent (e.g., an aqueous fluid), which permeates the first layer and dissolves the soluble portions of the second layer.
  • a solvent e.g., an aqueous fluid
  • the portions of the first layer that received radiation can then be removed, creating an imagewise lithographic pattern on the printing member.
  • the invention involves a printing member having an imaging layer which, in response to heat, undergoes a transition from an insoluble state to a soluble state, and a substrate thereunder.
  • the imaging layer and the substrate can have the same or opposite affinities for ink and/or a liquid to which ink will not adhere.
  • the transition that the imaging layer undergoes may involve a transition from a crystalline state to an amorphous state.
  • the substrate may be fabricated from a metal or a polymer.
  • the imaging layer may contain a material, such as a pigment and/or a dye, that absorbs imaging radiation.
  • the printing member contains an intermediate layer between the imaging layer and the substrate.
  • the imaging and intermediate layers have opposite affinities for ink and/or a liquid to which ink will not adhere.
  • the printing member may contain a top layer above the imaging layer that is permeable to a solvent, is transparent to imaging radiation, and has the same affinity as the imaging layer for ink and/or a liquid to which ink will not adhere.
  • the invention involves a method of imaging the lithographic printing member described above.
  • the printing member is exposed to imaging radiation in an imagewise pattern, which causes the portions of the imaging layer that receive the radiation to undergo a transition from an insoluble state to a soluble state.
  • the printing member is next subjected to an aqueous fluid, which dissolves the soluble portions of the second layer.
  • the portions of the imaging layer that received radiation can then be removed, creating an imagewise lithographic pattern on the printing member.
  • plate or “member” refers to any type of printing member or surface capable of recording an image defined by regions exhibiting differential affinities for ink and/or fountain solution.
  • Suitable configurations include the traditional planar or curved lithographic plates that are mounted on the plate cylinder of a printing press, but can also include seamless cylinders (e.g., the roll surface of a plate cylinder), an endless belt, or other arrangement.
  • the term "hydrophilic" is used in the printing sense to connote a surface affinity for a fluid which prevents ink from adhering thereto.
  • Such fluids include water for conventional ink systems, aqueous and non-aqueous dampening liquids, and the non-ink phase of single-fluid ink systems.
  • a hydrophilic surface in accordance herewith exhibits preferential affinity for any of these materials relative to oil-based materials.
  • FIG. 1 is an enlarged sectional view of an embodiment of a printing member according to the invention that contains a first layer, a second layer, and a substrate.
  • FIG. 2 is an enlarged sectional view of the printing member of FIG. 1, wherein only a portion of the second layer exposed to imaging radiation undergoes a transition.
  • FIG. 3 is an enlarged sectional view of an embodiment of a printing member according to the invention that contains a first layer, a second layer which includes a plurality of sub-layers, and a substrate.
  • FIG. 4 is an enlarged sectional view of an embodiment of a printing member according to the invention that contains a first layer, a second layer, a third layer, and a substrate.
  • FIG. 5 is an enlarged sectional view of an embodiment of a printing member according to the invention that contains a top layer, a first layer, a second layer, and a substrate.
  • FIG. 6 is an enlarged sectional view of an embodiment of a printing member according to the invention that contains a top layer, a first layer, a second layer, a third layer, and a substrate.
  • FIG. 7 is an enlarged sectional view of an embodiment of a printing member according to the invention that contains an imaging layer and a substrate.
  • FIGS. 8 and 10 are enlarged sectional views of an embodiment of a printing member according to the invention that contains an imaging layer, an intermediate layer, and a substrate.
  • FIG. 9 is an enlarged sectional view of an embodiment of a printing member according to the invention that contains a top layer, an imaging layer, and a substrate.
  • FIG. 10 is an enlarged sectional view of an embodiment of a printing member according to the invention that contains a top layer, an imaging layer, an intermediate layer, and a substrate.
  • FIGS. 11A-11C are enlarged sectional views of the printing member of FIG. 1 illustrating an imaging mechanism according to the invention.
  • FIGS. 12A-12C are enlarged sectional views of the printing member of FIG. 1 illustrating another imaging mechanism according to the invention.
  • FIGS. 13A-13B are enlarged sectional views of the printing member of FIG. 7 illustrating an imaging mechanism according to the invention.
  • FIGS. 14A-14C are enlarged sectional views of the printing member of FIG. 8 illustrating an imaging mechanism according to the invention.
  • FIGS. 15A-15C are enlarged sectional views of the printing member of FIG. 8 illustrating another imaging mechanism according to the invention.
  • the drawings and elements thereof may not be drawn to scale.
  • An imaging apparatus suitable for use in conjunction with the present printing members includes at least one laser device that emits in the region of maximum plate responsiveness, i.e., whose ⁇ max closely approximates the wavelength region where the plate absorbs most strongly.
  • Specifications for lasers that emit in the infrared (IR) or near-IR region are fully described in U.S. Patent Nos. Re. 35,5 12 ("the '512 patent”) and 5,385,092 ("the '092 patent”), the entire disclosures of which are hereby incorporated by reference. Lasers emitting in other regions of the electromagnetic spectrum are well-known to those skilled in the art. Suitable imaging configurations are also set forth in detail in the '512 and '092 patents.
  • laser output can be provided directly to the plate surface via lenses or other beam-guiding components, or transmitted to the surface of a blank printing plate from a remotely sited laser using a fiber-optic cable.
  • a controller and associated positioning hardware maintain the beam output at a precise orientation with respect to the plate surface, scan the output over the surface, and activate the laser at positions adjacent selected points or areas of the plate.
  • the controller responds to incoming image signals corresponding to the original document or picture being copied onto the plate to produce a precise negative or positive image of that original.
  • the image signals are stored as a bitmap data file on a computer. Such files may be generated by a raster image processor ("RIP") or other suitable means.
  • RIP raster image processor
  • a RIP can accept input data in page-description language, which defines all of the features required to be transferred onto the printing plate, or as a combination of page-description language and one or more image data files.
  • the bitmaps are constructed to define the hue of the color as well as screen frequencies and angles.
  • Other imaging systems such as those involving light valving and similar arrangements, can also be employed; see, e.g., U.S. Patent Nos. 4,577,932; 5,517,359; 5,802,034; and 5,861,992, the entire disclosures of which are hereby incorporated by reference.
  • image spots may be applied in an adjacent or in an overlapping fashion.
  • the imaging apparatus can operate on its own, functioning solely as a platemaker, or can be incorporated directly into a lithographic printing press. In the latter case, printing may commence immediately after application of the image to a blank plate, thereby reducing press set-up time considerably.
  • the imaging apparatus can be configured as a flatbed recorder or as a drum recorder, with the lithographic plate blank mounted to the interior or exterior cylindrical surface of the drum.
  • the exterior drum design is more appropriate to use in situ, on a lithographic press, in which case the print cylinder itself constitutes the drum component of the recorder or plotter.
  • the requisite relative motion between the laser beam and the plate is achieved by rotating the drum (and the plate mounted thereon) about its axis and moving the beam parallel to the rotation axis, thereby scanning the plate circumferentially so the image "grows" in the axial direction.
  • the beam can move parallel to the drum axis and, after each pass across the plate, increment angularly so that the image on the plate "grows" circumferentially.
  • an image corresponding (positively or negatively) to the original document or picture will have been applied to the surface of the plate.
  • the beam is drawn across either axis of the plate, and is indexed along the other axis after each pass.
  • the requisite relative motion between the beam and the plate may be produced by movement of the plate rather than (or in addition to) movement of the beam.
  • the writing array is then shifted, after completion of each pass across or along the plate, a distance determined by the number of beams emanating from the array, and by the desired resolution (i.e., the number of image points per unit length).
  • Off-press applications which can be designed to accommodate very rapid scanning (e.g., through use of high-speed motors, mirrors, etc.) and thereby utilize high laser pulse rates, can frequently utilize a single laser as an imaging source.
  • FIGS. 1-3 illustrate embodiments 100, 200 of printing members according to the invention that include a solvent-permeable first layer 102, a second layer 104 that undergoes a transition in response to heat, and a substrate 106.
  • FIG. 4 illustrates a variation 210 that includes a third layer 118 located between the second layer 104 and the substrate 106.
  • FIG. 5 illustrates yet another variation 220 that includes a solvent-permeable top layer 120 that is transparent to imaging radiation.
  • FIG. 6 illustrates a third variation 230 that includes both a third layer 118 and a solvent-permeable top layer 120.
  • the first layer 102 includes a polymer that is permeable to a solvent such as water and yet resistant to solubilization by such solvents.
  • this layer acts as a protective barrier above the second layer 104 and, if it is the top layer of the printing member, exhibits a lithographic affinity opposite to that of at least one layer below; for example, the first layer 102 may be oleophilic or hydrophilic.
  • the first layer 102 may be transparent to imaging radiation, or may instead absorb imaging radiation so as to impart heat to the second layer 104, facilitating its transition. Polymers utilized in this layer should exhibit good adhesion to the second layer 104 and be highly wear-resistant. A cross-linking agent may be added to the first layer 102 to enhance these characteristics.
  • Suitable polymers may be either water-based or solvent-based and can be oleophilic or hydrophilic.
  • the first layer 102 may (but again, need not) include a material that absorbs imaging radiation and transfers thermal energy to the second layer 104.
  • Suitable polymers for an oleophilic first layer 102 include, but are not limited to, polyurethanes, cellulosic polymers such as nitrocellulose, polycyanoacrylates, and epoxy polymers.
  • polyurethane-based materials are typically extremely tough and may have thermosetting or self-curing capability.
  • the first layer 102 may also be formed from a combination of one or more polymers, such as an epoxy polymer combined with a polyurethane polymer in the presence of a crosslinking agent and a catalyst, for example.
  • Suitable polymers for a hydrophilic first layer 102 include, but are not limited to, starch, dextran, alginic acid, and hydroxyethyl cellulose.
  • suitable absorbing materials can include a wide range of dyes and pigments, such as carbon black, nigrosine-based dyes, phthalocyanines (e.g., aluminum phthalocyanine chloride, titanium oxide phthalocyanine, vanadium (IV) oxide phthalocyanine, and the soluble phthalocyanines supplied by Aldrich Chemical Co., Milwaukee, WI), naphthalocyanines, iron chelates, nickel chelates, oxoindolizines, iminium salts, and indophenols, for example. Any of these materials may be dispersed in a prepolymer before cross-linking into a final film.
  • phthalocyanines e.g., aluminum phthalocyanine chloride, titanium oxide phthalocyanine, vanadium (IV) oxide phthalocyanine, and the soluble phthalocyanines supplied by Aldrich Chemical Co., Milwaukee, WI
  • naphthalocyanines e.g., iron chelates, nickel chelates,
  • the absorber may be a chromophore chemically integral with the polymer backbone; see, e.g., U.S. Patent No. 5,310,869.
  • the absorbing material should minimally affect adhesion between the first layer 102 and adjacent layers.
  • Surface-modified carbon-black pigments sold under the trade designation CAB-O-JET 200 by Cabot Corporation, Bedford, MA are found to minimally disrupt adhesion at loading levels that provide adequate sensitivity for heating.
  • Another suitable carbon-black pigment is BON JET BLACK CW-1, available from Orient Corporation, Springfield, IN J.
  • An exemplary first layer 102 may be prepared by mixing and coating methods known in the art, for example, combining a polyurethane polymer, an IR absorbing material (e.g., CAB-O-JET 200 carbon black), and hexamethoxy-methylmelamine crosslinking agent in a suitable solvent, followed by the addition of a suitable amine-blocked p-toluenesulfonic acid catalyst to form the finished coating mix.
  • the coating mix is then applied to the second layer 104 using one of the conventional methods of coating application, such as wire-wound rod coating, reverse roll coating, gravure coating, or slot die coating, and subsequently dried to remove the volatile liquids and to form a coating layer.
  • the first layer 102 is coated in this invention typically at a thickness in the range of from about 0.1 to about 2O microns and more preferably in the range of from about 0.1 to about 0.25 micron. After coating, the layer is dried and preferably cured at a temperature of between 145° C and 165° C.
  • Second Layer 104 The second layer 104 layer captures the image on the printing member by undergoing a phase change or other physico-chemical transition from an insoluble state to a soluble state in response to heat. Polymers utilized in this layer should exhibit good adhesion to the first layer 102 above and to the substrate 106 or the third layer 118 below, and be highly wear-resistant.
  • the second layer 104 may also include a material that absorbs imaging radiation.
  • the transition the second layer 104 undergoes in response to heat may involve a transition from an insoluble, crystalline state to a soluble, amorphous state.
  • the transition is reversible, which allows a printing member according to the invention to be "erased” and re-imaged. Erasure may be accomplished, for example, by heating an imaged plate in an oven and allowing it to cool slowly. It is believed that heating and slow cooling allows for recrystallization of the second layer 104 back to its insoluble state. Once cooled, the plate can be re-exposed to imaging radiation, and the new image will be revealed without any evidence of the first image. This "erasing" procedure can be repeated more than once.
  • the unimaged portions of the second layer 104 withstand repeated application of fountain solution during printing without substantial degradation or solubilization.
  • degradation of the second layer 104 may take the form of swelling of the layer and/or loss of adhesion to adjacent layers. This swelling and/or loss of adhesion may deteriorate the printing quality and dramatically shorten the press life of the printing member.
  • One test of withstanding the repeated application of fountain solution during printing is a wet rub resistance test. Satisfactory results in withstanding the repeated application of fountain solution and not being excessively soluble in water or in a cleaning solution are the retention of the 3% dots in the wet rub resistance test.
  • polymeric materials suitable for the second layer 104 include natural and non-natural polymers having exposed polar moieties such as hydroxyl or carboxyl groups.
  • suitable polymers include, but are not limited to, polyethylene derivatives (such as polyethylene oxide), cellulose derivatives (such as hydroxyethyl cellulose and carboxymethyl cellulose), polyvinyl derivatives (such as polyvinyl alcohol and polyvinyl ether), polysaccharides (such as dextrin, dextran, and starch derivatives), polyglycolides, gelatines, and polyols, particularly crystalline.
  • Suitable crystalline polyols include polyoxyalkylene polyols, the alkylene portion of which is a straight chain such as poly(oxyethylene) diol and poly(oxytetramethylene) diol; polyester polyols which are the reaction products of polyol(s) having from 2 to about 12 methylene groups and polycarboxylic acid(s) having from two to about 12 methylene groups; and polyester polyols made by ring-opening polymerization of lactones such as ⁇ -caprolactone; and blends thereof.
  • Preferred crystalline polyols include poly(oxytetramethylene) diol, polyhexamethylene adipate diol (made by reacting an excess of 1,6-hexarnethylene diol and adipic acid), polyhexamethylene sebacate diol (made by reacting an excess of 1,6-hexamethylene diol and sebacic acid), and polyhexamethylene dodecanedioate diol (made by reacting an excess of 1,6-hexamethylene diol and dodecanedioic acid).
  • Examples of commercially available crystalline polyols include, for example, poly(oxytetramethylene) polyols sold under the tradename TERATHANE (available from E.I.
  • the second layer 104 includes polyvinyl alcohol.
  • Polymers with relatively low degrees of crystallinity may also be suitable for use in the second layer. For example, heating a polymer above its melting point followed by slow cooling may enhance the crystallinity of the polymer.
  • reversibly cross-linking a polymer may lead to a more crystalline structure.
  • a high molecular weight polyacrylamide may be reversibly cross-linked via hydrogen bonding or multi-valent metals to form a water-insoluble, partially-crystalline state. Heat causes the cross-linked polymer to change phase from the water-insoluble, crystalline state to a water-soluble, amorphous state, allowing for image capture on the printing member.
  • cross-linking can be used to control resolubility, filler pigments to modify and/or control rewettability, and pigments and/or dyes to impart absorbance of laser energy.
  • fillers such as TiO 2 pigments, zirconia, silicas and clays are particularly useful in imparting rewettability without resolubility.
  • the second layer 104 contains a zirconium crosslinking agent, preferably ammonium zirconyl carbonate.
  • the second layer 104 may contain a material tihat absorbs imaging radiation.
  • Near-IR absorbers for second layers 104 based on polyvinyl alcohol include conductive polymers, e.g., polyanilines, polypyrroles, poly-3,4-ethylenedio. ypyrroles, polythiophenes, and poly-3,4-ethylenedioxythiophenes. As polymers, these are incorporated into the second layer 104 in the form of dispersions, emulsions, colloids, etc. due to their limited solubility. Alternatively, they can be formed in situ from monomeric components included in the second layer 104 as cast or applied to the second layer 104 subsequent to the curing process, i.e., by a post-impregnation or saturation process.
  • conductive polymers e.g., polyanilines, polypyrroles, poly-3,4-ethylenedio. ypyrroles, polythiophenes, and poly-3,4-ethylenedioxythiophenes.
  • these are incorporated into the second layer 104 in the
  • the catalyst for polymerization conveniently provides the "dopant" that establishes conductivity.
  • Certain inorganic absorbers, dispersed within the polymer matrix, also serve particularly well in connection with second layers 104 based on polyvinyl alcohol. These include TiON, TiCN, tungsten oxides of chemical formula WO 3 . x , where 0 ⁇ x ⁇ 0.5 (with 2.1 ⁇ x ⁇ 2.9 being preferred), and vanadium oxides of chemical formula V 2 O 5 . x , where 0 ⁇ x ⁇ 1.0 (with V 6 O] 3 being preferred).
  • Suitable absorbing materials include dyes and pigments, such as carbon black, nigrosine-based dyes, phthalocyanines (e.g., aluminum phthalocyanine chloride, titanium oxide phthalocyanine, vanadium (IV) oxide phthalocyanine, and the soluble phthalocyanines supplied by Aldrich Chemical Co., Milwaukee, WI), naphthalocyanines, iron chelates, nickel chelates, oxoindolizines, iminium salts, and indophenols, for example.
  • the second layer 104 is typically coated at at-hickness in the range of from about 0.1 to about 40 microns and more preferably in the range of from about 0.1 to about 0.5 micron.
  • the layer is dried and subsequently cured at a temperature between 135° C and
  • Lithographic printing members include a first layer 102 that has an affinity for ink and/or a liquid to which ink will not adhere that is opposite that of the substrate 106 and/or the optional third layer 118. In these embodinnents, the second layer 104 can have either the same or opposite affinity as the first layer 102 for ink and/or a liquid to which ink will not adhere.
  • a second layer 104 and a first layer 102 of like affinities because the second layer 104 will accept or reject ink in the same manner as the overlying first layer 102 in those areas where the first layer 102 is damaged during handling or the printmaking process, thus maintaining print quality and prolonging the press life of the printing member.
  • only a portion of the second layer 104 exposed to imaging radiation undergoes the transition. For example, with reference to FIG.
  • the imaging radiation may cause a first portion 108 of the second layer 104 (e.g., a portion of the second layer 104 near the first layer 102) to transition to a soluble state, while a second portion 110 of the second layer 104 (e.g., a portion of the second layer 104 near the substrate 106) remains in an insoluble state.
  • the imaging radiation can cause a gradient of transformation to occur within the exposed portions of the second layer 104, whereby the second layer 104 changes gradually from substantially insoluble to highly soluble, with increasing intermediate solubility in between.
  • the first layer 102 and the second layer 104 have opposite affinities for ink and/or a liquid to which ink will not adhere, and the first layer 102, the substrate 106, and/or the optional third layer 112 may have the same or opposite affinities.
  • the imaging radiation source is adjusted (e.g. - by changing the frequency or the duration of the imaging pulse) to deliver only enough energy to cause a transition in a portion of the second layer 104.
  • the radiation source can be tuned to deliver a lower laser flux density (e.g., 75-175 mJ/cm 2 ) to cause only a portion of the second layer to change phase.
  • a lower laser flux density e.g. 75-175 mJ/cm 2
  • Other embodiments involve manipulating the composition of the lithographic imaging member itself. For example, the concentration of radiation-absorbing material in the second layer 104 may be reduced, or a limited-stability absorber may be used, so that less heat is absorbed by the second layer 104.
  • Limited-stability absorbers are compounds that break down in the presence of imaging radiation to form fragments that have little or no absorption capacity, thus imposing a ceiling on the temperature the second layer 104 may reach in response to the imaging radiation.
  • the second layer 104 can be formed without any radiation-absorbing material at all, instead relying upon conduction from a first layer 102 that is able to convert the imaging radiation to heat. In this manner, the topmost portion of the second layer 104 near the first layer 102 is exposed to the heat, while lower portions of the second layer 104 near the substrate 106 receive little or no heat, resulting in solubility differences throughout the second layer 104.
  • the second layer 104 contains a gradient of radiation-absorbing material that increases with distance from the substrate 106.
  • One approach for forming such a gradient is to apply the second layer 104 to the substrate 106, and then add the radiation- absorbing material to the top of the second layer 104 before it cures.
  • the radiation-absorbing material can then diffuse into the second layer 104, either due to gravity or by the application of an external force, creating a gradient of radiation-absorbing material throughout the second layer 104.
  • a gradient is produced by creating an initial uniform dispersion of the radiation-absorbing material, followed by controlled settling to concentrate the radiation-absorbing material toward one of the interfaces of the second layer 104.
  • the second layer 104 can be a graded layer that is built up in successive stages. Referring to the embodiment 200 shown in FIG.
  • the second layer 104 includes a series of sub-layers 112, 114, and 116, each containing a different concentration of radiation-absorbing material.
  • the first sub-layer 112 can be pre-mixed with the radiation-absorbing material prior to applying it to the substrate 106, or the radiation-absorbing material can be added after the first sub-layer 112 has been applied to the substrate 106 but before the first sub-layer 112 has cured.
  • the application process is repeated for subsequent sub-layers 114 and 116, with each subsequent sub-layer including a higher concentration of radiation-absorbing material than the previous.
  • Each subsequent sub-layer can be applied either before or after the previous sub-layer has cured.
  • the second layer 104 in the illustrative embodiment 200 contains three sub-layers, it should be understood that a second layer 104 can include any number of sub-layers.
  • different radiation-absorbing materials that have different absorption capacities can be included in the various sub-layers of the second layer 104 to produce the desired gradient effect.
  • dyes such as phthalocyanines and naphthalocyanines may have lower absorption capacities than pigments such as carbon black.
  • both the imaging radiation source and the lithographic printing member can be manipulated in combination to produce the desired transition in the second layer 104.
  • substrate 106 provides dimensionally stable mechanical support to the printing member and may dissipate heat accumulated in the second layer 104 to prevent its ablation.
  • Suitable substrate materials include, but are not limited to, alloys of aluminum, chromium, and steel, which may have another metal such as copper plated over one surface. Preferred thicknesses range from 0.004 to 0.02 inch, with thicknesses in the range 0.005 to 0.012 inch being particularly preferred.
  • substrate 106 may be paper or a polymer film (e.g., polyesters such as polyethylene terephthalate and polyethylene naphthalate, polycarbonates, polyurethane, acrylic, polyamide, or phenolic polymers).
  • Preferred thicknesses for such films range from 0.003 to 0.02 inch, with thicknesses in the range of 0.005 to 0.015 inch being particularly preferred.
  • a primer coating between the second layer 104 and the substrate 106; suitable formulations and application techniques for such coatings are disclosed, for example, in U.S. Patent No. 5,339,737, the entire disclosure of which is hereby incorporated by reference.
  • any of the embodiments 100-230 may be fabricated with a metal, paper, polymer or other substrate material.
  • Non-image areas of the printing member have an affinity opposite to that of the image areas for ink and/or a liquid to which ink will not adhere.
  • the first layer 102 and the substrate 106 have opposite lithographic affinities .
  • the first layer 102 and the substrate 106 need not have opposite lithographic affinities, because the first and third layers 102 and 118 have opposite affinities, as described below.
  • the third layer 118 is typically not soluble in aqueous solutions and is not removed during the imaging process, it can still be scratched or damaged during the printmaking process.
  • a substrate 106 of like affinity will accept or reject ink in the same manner as the overlying third layer 118 in those areas where the third layer 118 is damaged, thus maintaining print quality and prolonging the press life of the printing member.
  • the first layer 102 and the substrate 106 need not have opposite lithographic affinities, because the first and second layers 102 and 104 have opposite affinities, as described above.
  • a substrate 106 and a second layer 104 of like affinities to promote adhesion and to accommodate damage to the second layer 104 without loss of performance.
  • a metal substrate must undergo special treatment in order to provide a hydrophilic surface. Any number of chemical or electrical techniques, in some cases assisted by the use of fine abrasives to roughen the surface, may be employed for this purpose. For example, electrograining involves immersion of two opposed aluminum plates (or one plate and a suitable counterelectrode) in an electrolytic cell and passing alternating current between them. The result of this process is a finely pitted surface topography that readily adsorbs water.
  • a structured or grained surface can also be produced by controlled oxidation, a process commonly called “anodizing.”
  • An anodized aluminum substrate consists of an unmodified base layer and a porous, “anodic" aluminum oxide coating thereover; this coating readily accepts water. However, without further treatment, the oxide coating would lose wettability due to further chemical reaction.
  • Anodized plates are, therefore, typically exposed to a silicate solution or other suitable (e.g., phosphate) reagent that stabilizes the hydrophilic character of the plate surface.
  • silicate treatment the surface may assume the properties of a molecular sieve with a high affinity for molecules of a definite size and shape — including, most importantly, water molecules.
  • the treated surface also promotes adhesion to an overlying second layer 104 in embodiments that do not include an intervening third layer 118.
  • Preferred hydrophilic substrate materials include aluminum that has been mechanically, chemically, and/or electrically grained with or without subsequent anodization. In addition, some metal layers need only be cleaned, or cleaned and anodized, to present a sufficiently hydrophilic surface.
  • a wide variety of papers may be utilized as a substrate 106. Typically, papers are saturated with a polymeric treatment to improve dimensional stability, water resistance, and strength during the wet lithographic printing.
  • suitable polymeric substrates 106 include, but are not limited to, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polycarbonates, polystyrene, polysulfones, and cellulose acetate.
  • Polymeric substrates 106 can further comprise a hydrophilic or oleophilic coating applied to at least one surface of a polymer film.
  • a preferred polymeric substrate is polyethylene terephthalate film, such as the polyester films available under the trademarks of MYLAR and MELINEX from E. I. duPont de Nemours Co., Wilmington, DE, for example.
  • 2.4 Optional Third layer 118 With reference to FIGS.
  • the optional third layer 118 is located between the substrate 106 and the second layer 104 and provides a thermal barrier during laser exposure to prevent heat loss and possible damage to the substrate 106.
  • the third layer 118 can be hydrophilic or oleophilic and should adhere well to the substrate 106 and to the second layer 104.
  • the first layer 102 and the third layer 118 have opposite affinities for ink and/or a liquid to which ink will not adhere.
  • the first layer 102 and the third layer 118 need not have opposite lithographic affinities, because the first and second layers 102, 104 have opposite affinities, as described above.
  • the remaining portion of the second layer 104 is not soluble in aqueous solutions and is not removed during the imaging process, it can still be scratched or damaged during the printmaking process.
  • a third layer 118 of like affinity will accept or reject ink in the same manner as the overlying remnants of the second layer 104 in those areas where the second layer 104 is damaged, thus maintaining print quality and prolonging the press life of the printing member.
  • the third layer 118 withstands repeated application of fountain solution during printing without substantial degradation or solubilization.
  • degradation of the third layer 118 may take the form of swelling of the layer and/or loss of adhesion to the second layer 104 and/or to the substrate 106. This swelling and/or loss of adhesion may deteriorate the printing quality and dramatically shorten the press life of the printing member.
  • a suitable third layer 118 will retain the 3% dots in the wet rub resistance test, as described above.
  • polymeric materials suitable for a hydrophilic third layer 118 include those having exposed polar moieties such as hydroxyl or carboxyl groups such as various cellulosics modified to incorporate such groups, and polyvinyl alcohol polymers, for example.
  • polymeric reaction products of polyvinyl alcohol and crosslinking agents such as glyoxal, gluteraldehyde, p-toluene sulfonic acid, zinc carbonate, and the like are well known in the art.
  • the polymeric reaction products of polyvinyl alcohol and hydrolyzed tetramethylorthosilicate or tetraethylorthosilicate are described in U.S. Pat. No. 3,971,660.
  • Suitable polyvinyl alcohol-based coatings for use in third layers 118 include, but are not limited to, combinations of AIR VOL 125 polyvinyl alcohol; BACOTE 20, a trademark for an ammonium zirconyl carbonate solution available from Magnesium Elektron, Flemington, NJ; glycerol, available from Aldrich Chemical, Milwaukee, WI; and TRITON X-100, a trademark for a surfactant available from Rohm & Haas, Philadelphia, PA.
  • Typical amounts of BACOTE 20 utilized in crosslinking polymers are less than 5% by weight of the weight of the polymers.
  • BACOTE 20 significantly increased levels provide significant improvements in durability, in the ease of cleaning the laser-exposed areas, in adhesion to the ink-accepting areas of the plate during long press runs, and in the fine image resolution and printing quality that can be achieved.
  • zirconium compounds such as BACOTE 20 have a high affinity for water when they are dried and cured at high loadings in a crosslinked coating containing polyvinyl alcohol.
  • the high levels of BACOTE 20 also provide a hydrophilic third layer 118 which interacts with a subsequent coating application of the second layer 104 to further increase the insolubility and resistance to damage by laser radiation and by contact with water, a cleaning solution, or a fountain solution.
  • a hydrophilic third layer 118 comprises ammonium zirconyl carbonate in an amount greater than 10% by weight based on the total weight of the polymers present in the layer. In another embodiment, a hydrophilic third layer 118 comprises ammonium zirconyl carbonate in an amount of 20 to 50% by weight based on the total weight of polymers present in the layer. Examples of materials suitable for oleophilic third layers 118 include crosslinked polymer forms of polyurethanes, acrylics, polyamides, and phenolics, for example.
  • the third layer 118 typically has a thickness in the range of from about 1 to about 40 microns and more preferably in the range of from about 2 to about 25 microns.
  • the layer is dried and subsequently cured at a temperature between 135° C and 185° C for between 10 seconds and 3 minutes, and more preferably at a temperature between 145° C and 165° C for between 30 seconds and 2 minutes.
  • the optional top layer 120 is located above the first layer 102 and is designed to be more robust on press and more scratch-resistant than the first layer 102, thus maintaining print quality and prolonging the press life of the printing member.
  • the top layer 120 includes a polymer that is permeable to water (or other solvent) and yet resistant to solubilization by aqueous solvents.
  • Polymers utilized in this layer are generally transparent to imaging radiation and have the same affinity as the first layer 102 for ink and/or a liquid to which ink will not adhere.
  • Suitable polymers for the top layer 120 include hydroxy-functional, carboxy- functional, or epoxy-functional polymers, for example. The polymers are cross-linked to a greater extent than those in the first layer 102 to provide added durability while maintaining sensitivity to the imaging radiation. 3.
  • Two-layer Lithographic Printing Members Referring to FIG. 7, another embodiment of a printing member shown at 240 includes an imaging layer 122 that undergoes a transition in response to heat, and a substrate 124, as described above.
  • FIG. 8 illustrates a variation 250 that includes an intermediate layer 126 disposed between the imaging layer 122 and the substrate 124.
  • FIG. 9 illustrates yet another variation 260 that includes a top layer 128 that is permeable to water (or other solvent) and transparent to imaging radiation, as described above.
  • FIG. 10 illustrates a third variation 270 that includes both an intermediate layer 126 and a permeable top layer 128.
  • the imaging layer 122 layer captures the image on the printing member by undergoing transition from an insoluble state to a soluble state in response to heat.
  • the imaging layer 122 can be oleophilic or hydrophilic and can include a material that absorbs imaging radiation. Polymers utilized in this layer should exhibit good adhesion to adjacent layers and be highly wear-resistant.
  • the non-imaged portions of the imaging layer 122 withstand repeated application of fountain solution during printing without substantial degradation or solubilization.
  • the transition that the imaging layer 122 undergoes in response to heat may be from an insoluble, crystalline state to a soluble, amorphous state. In some embodiments, substantially all of the imaging layer 122 exposed to the imaging radiation undergoes the transition from an insoluble state to a soluble state. In other embodiments, only a portion of the imaging layer 122 exposed to the imaging radiation undergoes the transition.
  • the transition can be reversible (e.g., a phase change), which allows a printing member according to the invention to be "erased" and re-imaged, as described above.
  • suitable polymeric materials for use in the imaging layer 122 include those having exposed polar moieties such as hydroxyl or carboxyl groups, various cellulosics modified to incorporate such groups, and polyvinyl alcohol polymers, for example.
  • the imaging layer 122 includes polyvinyl alcohol.
  • cross-linking can be used to control resolubility, filler pigments to modify and/or control rewettability, and pigments and/or dyes to impart absorbance of laser energy.
  • fillers such as Ti0 2 pigments, zirconia, silicas and clays are particularly useful in imparting rewettability without resolubility.
  • the imaging layer 122 contains a zirconium crosslinking agent, preferably ammonium zirconyl carbonate.
  • Suitable materials for absorbing IR or near-IR imaging radiation include a wide range of dyes and pigments, such as carbon black, nigrosine-based dyes, phthalocyanines (e.g., aluminum phthalocyanine chloride, titanium oxide phthalocyanine, vanadium (IV) oxide phthalocyanine, and the soluble phthalocyanines supplied by Aldrich Chemical Co., Milwaukee, WI), naphthalocyanines, iron chelates, nickel chelates, oxoindolizines, iminium salts, and indophenols, for example.
  • phthalocyanines e.g., aluminum phthalocyanine chloride, titanium oxide phthalocyanine, vanadium (IV) oxide phthalocyanine, and the soluble phthalocyanines supplied by Aldrich Chemical Co., Milwaukee, WI
  • naphthalocyanines iron
  • any of these materials may be dispersed in a prepolymer before cross-linking into a final film.
  • the absorbing material should minimally affect adhesion between the imaging layer 122 and adjacent layers.
  • Surface-modified carbon-black pigments sold under the trade designation CAB-O-JET 200 by Cabot Corporation, Bedford, MA are found to minimally disrupt adhesion at loading levels providing adequate sensitivity for heating.
  • Another suitable carbon-black pigment is BONJET BLACK CW-1, available from Orient Corporation, Springfield, NJ.
  • Near-IR absorbers for imaging layers 122 based on polyvinyl alcohol include conductive polymers, e.g., polyanilines, polypyrroles, poly-3,4-ethylenedioxypyrroles, polythiophenes, and poly-3,4-ethylenedioxythiophenes. As polymers, these are incorporated into the imaging layer 122 in the form of dispersions, emulsions, colloids, etc. due to their limited solubility. Alternatively, they can be formed in situ from monomeric components included in the imaging layer 122 as cast or applied to the imaging layer 122 subsequent to the curing process — i.e., by a post-impregnation or saturation process.
  • conductive polymers e.g., polyanilines, polypyrroles, poly-3,4-ethylenedioxypyrroles, polythiophenes, and poly-3,4-ethylenedioxythiophenes.
  • these are incorporated into the imaging layer 122 in the form of dispersions
  • the catalyst for polymerization conveniently provides the "dopant" that establishes conductivity.
  • Certain inorganic absorbers, dispersed within the polymer matrix, also serve particularly well in connection with imaging layers 122 based on polyvinyl alcohol. These include TiON, TiCN, tungsten oxides of chemical formula WO 3 . x , where 0 ⁇ x ⁇ 0.5 (with 2.1 ⁇ x ⁇ 2.9 being preferred), and vanadium oxides of chemical formula V 2 0 5 - x , where 0 ⁇ x ⁇ 1.0 (with V 6 O] 3 being preferred).
  • the substrate 124 provides dimensionally stable mechanical support to the printing member and possibly dissipates heat accumulated in the imaging layer 122 to prevent its ablation.
  • the substrate 124 can be either hydrophilic or oleophilic.
  • the substrate 106 in any of the embodiments 240-270 may be fabricated using any of the materials and methods described above.
  • the imaging layer 122 and the substrate 124 have opposite affinities for ink and/or a liquid to which ink will not adhere.
  • an intermediate layer 126 e.g. FIGS.
  • the imaging layer 122 and the substrate 124 need not have opposite lithographic affinities, because the imaging layer 122 and the intermediate layer 126 have opposite affinities, as described below.
  • the intermediate layer 126 is typically not soluble in aqueous solutions and is not removed during the imaging process, it can still be scratched or damaged during the printmaking process.
  • a substrate 124 of like affinity will accept or reject ink in the same manner as the overlying intermediate layer 126 in those areas where the intermediate layer 126 is damaged, thus maintaining print quality and prolonging the press life of the printing member.
  • the optional intermediate layer 126 is located between the substrate 124 and the imaging layer 122.
  • the intermediate layer 126 can be either hydrophilic or oleophilic, provided that it has an affinity opposite to that of the imaging layer 122 for at least one of ink and a liquid to which ink will not adhere. It should adhere well to the substrate 124 and to the imaging layer 122 and should withstand repeated application of fountain solution during printing without substantial degradation or solubilization.
  • the intermediate layer 126 is equivalent to the third layer 118 described above.
  • the intermediate layer 126 provides a thermal barrier during laser exposure to prevent heat loss and possible damage to the substrate 124.
  • the intermediate layer 126 absorbs imaging radiation so as to impart heat to the imaging layer 122, facilitating its transition.
  • the intermediate layer 126 may (but need not) include a material that absorbs imaging radiation and transfers thermal energy to the imaging layer 122.
  • suitable absorbing materials can include a wide range of dyes and pigments, as described above.
  • the absorbing material should minimally affect adhesion between the intermediate layer 124 and adjacent layers.
  • the intermediate layer 126 in any of the embodiments 240-270 may be fabricated using any of the materials and methods described above.
  • the optional top layer 128 is located above the imaging layer 122 and is designed to be more robust on press and more scratch-resistant than the imaging layer 122, thus maintaining print quality and prolonging the press life of the printing member.
  • the top layer 128 includes a polymer that is permeable to water (or other solvent) and yet resistant to solubilization by aqueous solvents. Polymers utilized in this layer should be transparent to imaging radiation and have the same affinity as the imaging layer 122 for ink and/or a liquid to which ink will not adhere.
  • the top layer 128 in any of the embodiments 240-270 may be fabricated using any of the materials and methods described above.
  • FIGS. 11A-11C illustrate the consequences of imaging an embodiment of printing member 100, wherein substantially all of the second layer 104 exposed to the imaging radiation changes phase.
  • the first layer 102 of the printing member 100 contains a material that absorbs imaging radiation.
  • the exposed area 130 of the first layer 102 absorbs the imaging pulse and converts the energy to heat.
  • the heat is transferred to the portion 132 of the second layer 104 immediately below the exposed area 130 of the first layer 102, causing substantially all of the portion 132 of the second layer 104 to change from an insoluble state to a soluble state.
  • a solvent (e.g., an aqueous fluid) applied to the printing member 100 post-imaging permeates the first layer 102 and dissolves the soluble portion 132 of the second layer 104.
  • the dissolved portion 132 of the second layer 104, along with the portion 130 of the first layer 102 that overlies it, can then be removed (e.g., by rubbing or as a consequence of the mechanical action that takes place during the print "make ready” process) to expose the substrate 106 below, as illustrated in FIG. 1 lC.
  • FIGS. 12A-12C illustrate the consequences of imaging another embodiment of the printing member 100, wherein only a portion of the second layer 104 exposed to the imaging radiation undergoes transition.
  • the first layer 102 of the printing member 100 contains a material that absorbs imaging radiation. As illustrated in FIG. 12A, the exposed area 130 of the first layer 102 absorbs the imaging pulse and converts the energy to heat. Referring to FIG. 12B, the heat is transferred to the second layer 104 immediately below the exposed area 130 of the first layer 102, causing only a portion 134 of the second layer 104 to change from an insoluble state to a soluble state.
  • An aqueous fluid applied to the printing member 100 post-imaging permeates the first layer 102 and dissolves the soluble portion 134 of the second layer 104. The dissolved portion 134 of the second layer 104, along with the portion 130 of the first layer 102 that overlies it, can then be removed (e.g.
  • the second layer 104 of the printing member 100 contains a material that absorbs imaging radiation.
  • the imaging pulse passes through the first layer 102 and is absorbed by the second layer 104, causing the transition described above.
  • both the first and second layers 102 and 104 contain absorbing material.
  • the exposed areas of the first layer 102 absorb the imaging pulse and convert the energy to heat, which is transferred to the second layer 104.
  • FIGS. 13A and 13B illustrate the consequences of exposing an embodiment of the printing member 240 to the output of an imaging laser.
  • the exposed portion 138 of the imaging layer 122 absorbs the imaging pulse and converts the energy to heat, causing the exposed portion 138 to change from an insoluble state to a soluble state.
  • a solvent e.g,. an aqueous fluid
  • a solvent applied to the printing member 250 post-imaging dissolves the soluble portion 138 of the imaging layer 122.
  • the dissolved portion 138 of the imaging layer 122 can then be removed to expose the substrate 124 below, as illustrated in FIG. 13B.
  • FIG. 14A-14C illustrate the consequences of exposing an embodiment of the printing member 250 to the output of an imaging laser.
  • the imaging layer 122 is transparent to the imaging radiation.
  • the exposed area 140 of the intermediate layer 126 absorbs the imaging pulse and converts the energy to heat.
  • the heat is transferred to the portion 142 of the imaging layer 122 immediately above the exposed area 140 of the intermediate layer 126, causing substantially all of the portion 142 of the imaging layer 122 to change from an insoluble state to a soluble state.
  • a solvent e.g., an aqueous fluid
  • FIGS. 15A-15C illustrate a variation of the process described in FIGS. 14A-14C, wherein only a portion 146 of the imaging layer 122 undergoes a transition in response to imaging radiation. As illustrated in FIG. 15A, the exposed area 144 of the intermediate layer 126 absorbs the imaging pulse and converts the energy to heat.
  • the heat is transferred to the imaging layer 122 immediately above the exposed area 144 of the intermediate layer 126, causing only a portion 146 of the imaging layer 122 to change from an insoluble state to a soluble state.
  • a solvent e.g., an aqueous fluid
  • applied to the printing member 260 post-imaging permeates the remaining insoluble portion 148 of the imaging layer 122 and dissolves the soluble portion 146.
  • the dissolved portion 146 of the imaging layer 122, along with the remaining insoluble portion 148 that overlies it, can then be removed (e.g. by rubbing or as a consequence of the mechanical action that takes place during the print "make ready” process) to expose the intermediate layer 126 below, as illustrated in FIG. 15C.
  • the imaging pulse delivers the proper amount of energy to the printing member to cause the desired transition.
  • the amount of energy required is a function of parameters such as laser power, the duration of the pulse, the intrinsic absorption of the heat-sensitive layer (as determined, for example, by the concentration of absorber therein), the thickness of the heat-sensitive layer, and the presence of a thermally conductive layer beneath the heat-sensitive layer. These parameters are readily determined by the skilled practitioner without undue experimentation. It will be seen that the foregoing techniques provide a basis for improved lithographic printing and superior plate constructions.

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  • Thermal Sciences (AREA)
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  • Manufacturing & Machinery (AREA)
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Abstract

Des transitions de solubilité plutôt que des mécanismes d'ablation facilitent l'extraction sélective de la couche d'imagerie d'une plaque lithographique, ce qui permet une imagerie avec des lasers de faible puissance qui n'ont pas besoin de mettre en oeuvre des niveaux d'énergie induisant l'ablation.
PCT/US2005/010193 2004-03-26 2005-03-25 Elements d'impression possedant des couches de transition de solubilite et procedes associes WO2005097502A1 (fr)

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JP2007505242A JP2007531019A (ja) 2004-03-26 2005-03-25 溶解度変化層を有する印刷部材及び関連する方法
AU2005231729A AU2005231729A1 (en) 2004-03-26 2005-03-25 Printing members having solubility-transition layers and related methods
CA002560644A CA2560644A1 (fr) 2004-03-26 2005-03-25 Elements d'impression possedant des couches de transition de solubilite et procedes associes
DE602005007336T DE602005007336D1 (de) 2004-03-26 2005-03-25 Druckglieder mit löslichkeitsübergangsschichten und verwandte verfahren
EP05731303A EP1732758B1 (fr) 2004-03-26 2005-03-25 Elements d'impression possedant des couches de transition de solubilite et procedes associes

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JP2005280073A (ja) * 2004-03-29 2005-10-13 Fuji Photo Film Co Ltd 平版印刷版の露光処理方法及びこの方法を実施する装置
DE602006011920D1 (de) * 2005-09-09 2010-03-11 Presstek Inc Druckglieder mit permeabilitätstransitionsschichten und verwandte verfahren
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ATE397529T1 (de) 2008-06-15
CA2560644A1 (fr) 2005-10-20
AU2005231729A1 (en) 2005-10-20
EP1732758A1 (fr) 2006-12-20
EP1732758B1 (fr) 2008-06-04
JP2007531019A (ja) 2007-11-01
DE602005007336D1 (de) 2008-07-17
US20050247226A1 (en) 2005-11-10

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